package levelloader
{
	import flash.utils.ByteArray;
	
	public class CustomBase64Decoder
	{
		private static const _encodeChars:Vector.<int> = InitEncoreChar();
		private static const _decodeChars:Vector.<int> = InitDecodeChar();
		
		public static function encode(data:ByteArray):String
		{
			var out:ByteArray = new ByteArray();
			//Presetting the length keep the memory smaller and optimize speed since there is no "grow" needed
			out.length = (2 + data.length - ((data.length + 2) % 3)) * 4 / 3; //Preset length //1.6 to 1.5 ms
			var i:int = 0;
			var r:int = data.length % 3;
			var len:int = data.length - r;
			var c:uint; //read (3) character AND write (4) characters
			var outPos:int = 0;
			while (i < len)
			{
				//Read 3 Characters (8bit * 3 = 24 bits)
				c = data[int(i++)] << 16 | data[int(i++)] << 8 | data[int(i++)];
				
				out[int(outPos++)] = _encodeChars[int(c >>> 18)];
				out[int(outPos++)] = _encodeChars[int(c >>> 12 & 0x3f)];
				out[int(outPos++)] = _encodeChars[int(c >>> 6 & 0x3f)];
				out[int(outPos++)] = _encodeChars[int(c & 0x3f)];
			}
			
			if (r == 1) //Need two "=" padding
			{
				//Read one char, write two chars, write padding
				c = data[int(i)];
				
				out[int(outPos++)] = _encodeChars[int(c >>> 2)];
				out[int(outPos++)] = _encodeChars[int((c & 0x03) << 4)];
				out[int(outPos++)] = 61;
				out[int(outPos++)] = 61;
			}
			else if (r == 2) //Need one "=" padding
			{
				c = data[int(i++)] << 8 | data[int(i)];
				
				out[int(outPos++)] = _encodeChars[int(c >>> 10)];
				out[int(outPos++)] = _encodeChars[int(c >>> 4 & 0x3f)];
				out[int(outPos++)] = _encodeChars[int((c & 0x0f) << 2)];
				out[int(outPos++)] = 61;
			}
			
			return out.readUTFBytes(out.length);
		}
		
		public static function decode(str:String):ByteArray
		{
			var c1:int;
			var c2:int;
			var c3:int;
			var c4:int;
			var i:int = 0;
			var len:int = str.length;
			
			var byteString:ByteArray = new ByteArray();
			byteString.writeUTFBytes(str);
			var outPos:int = 0;
			while (i < len)
			{
				//c1
				c1 = _decodeChars[int(byteString[i++])];
				if (c1 == -1)
					break;
				
				//c2
				c2 = _decodeChars[int(byteString[i++])];
				if (c2 == -1)
					break;
				
				byteString[int(outPos++)] = (c1 << 2) | ((c2 & 0x30) >> 4);
				
				//c3
				c3 = byteString[int(i++)];
				if (c3 == 61)
				{
					byteString.length = outPos
					return byteString;
				}
				
				c3 = _decodeChars[int(c3)];
				if (c3 == -1)
					break;
				
				byteString[int(outPos++)] = ((c2 & 0x0f) << 4) | ((c3 & 0x3c) >> 2);
				
				//c4
				c4 = byteString[int(i++)];
				if (c4 == 61)
				{
					byteString.length = outPos
					return byteString;
				}
				
				c4 = _decodeChars[int(c4)];
				if (c4 == -1)
					break;
				
				byteString[int(outPos++)] = ((c3 & 0x03) << 6) | c4;
			}
			byteString.length = outPos
			return byteString;
		}
		
		public static function InitEncoreChar():Vector.<int>
		{
			var encodeChars:Vector.<int> = new Vector.<int>(64, true);
			
			// We could push the number directly
			// but I think it's nice to see the characters (with no overhead on encode/decode)
			var chars:String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
			for (var i:int = 0; i < 64; i++)
			{
				encodeChars[i] = chars.charCodeAt(i);
			}
			
			return encodeChars;
		}
		
		public static function InitDecodeChar():Vector.<int>
		{
			
			var decodeChars:Vector.<int> = new <int>[
				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 
				52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, 
				-1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 
				15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, 
				-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 
				41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, 
				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1];
			
			return decodeChars;
		}
	
	}
}
	
	